Server.kt

package io.vertx.example.mqtt.simple

import io.vertx.kotlin.mqtt.*
import io.vertx.mqtt.MqttServer
import io.vertx.mqtt.MqttServerOptions

class Server : io.vertx.core.AbstractVerticle()  {
  override fun start() {

    var options = MqttServerOptions(
      port = 1883,
      host = "0.0.0.0")

    var server = MqttServer.create(vertx, options)

    server.endpointHandler({ endpoint ->

      println("connected client ${endpoint.clientIdentifier()}")

      endpoint.publishHandler({ message ->

        println("Just received message on [${message.topicName()}] payload [${message.payload()}] with QoS [${message.qosLevel()}]")
      })

      endpoint.accept(false)
    })

    server.listen({ ar ->
      if (ar.succeeded()) {
        println("MQTT server started and listening on port ${server.actualPort()}")
      } else {
        System.err.println("MQTT server error on start${ar.cause().getMessage()}")
      }
    })
  }
}